Balanced valve.



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UNITED STATES Patented June 9, 1903.

PATENT OFFICE.

BALANCED VALVE.

SPECIFICATION forming part of Letters Patent No.' 730,699, dated -T une 9, 1903. Application led April 3, 1903. Serial No. 150|880. (No model.)

To all whom it may conccrm- Be it known that I, DE WITT C. PREsCo'rT, a citizen of the United States, and a resident of Chicago, county of Cook, and State of Illinois, have invented certain new and useful Improvements in Balanced Valves, of which the following is a specification and which are illustrated in the accompanying drawings, forming a part thereof.

The invention relates to engine-Valves, and particularly to that class of single-acting valves used in connection with direct-steamfeed motors for sawmill-carriages.

The object of the invention is, primarily, to eliminate in valves of this 'character what is known in the trade as the kick-back, being a more or less vicious jerk of the valve immediately following its initial movement, particularly on a quick reversal of the motor, and causing a jar to the hand of the operator.

A further object is to provide a complete balance of a valve of this character.

The invention consists in the structure hereinafter fully described, and illustrated in the accompanying drawings, in which- Figure 1 is a detail of a sawmill feed-motor. Fig. 2 is a longitudinal central section of the valve through its cylinder and exhaust ports. Fig. 3 is a longitudinal central section on a plane perpendicular to that of Fig.

2, and Fig. 4 is a transverse section of the valve on the line 4 of Fig. 2.

The valve-casing is represented in Figs. 2 and 3 as without heads.

In motors of the type referred to a cylinder, as 24, is employed, which is as long as the range of travel of the carriage it is intended' to drive, and this cylinder is provided with a piston (not shown) having its rod 25 attached directly to the sawmill-carriage, as shown at 26. Usually such a motor is provided with two valves, as 10 and 23, one at each end, which are controlled by a single hand-lever, as 27, suitably located. Each of these valves serves-one end only of the cylinder, and consequently is what is known as a single-acting valve.

The valve-casing 10 is preferably cylindrical in form and may or may not be provided with heads, as 11 12. This casing is provided with-an induction-port 13, an exhaustport 14, and a cylinder-port v15, arranged inthe order named and each port opening to the chamber of the valve-casing annularly or, in other words, each port being continued in the inner face of the valvechamber by means of an annular channel, thereby providing for a complete lateral balancing of the valve as well as for large port area.

The valve proper, 16, is preferably in piston form and has a peripheral cavity 17 of sufficient length to so far overlap the three ports that it is in constant register with the cylinder-port 15.k A face-ring 15S-that is to say, a ring which forms part'of the peripheral face of the valvecrosses the cavity 17 intermediate of its ends and is carried by longitudinal ribs 19, rising from the bottom thereof and extending, if desired, the entire length of the cavity, as shown. The ring 18 is of sufficient width to approximately spanthe induction and exhaust ports simultaneously and is spaced apart from the end of the cavity 17 adjacent to the induction-port 13 a distance substantially equal to the width of the channel forming a continuation of that port, and the distance between the exhaust and cylinder ports is such that the face-ring 18 does not materially encroach upon the cylinder port when the induction-port is open. When the valve-casingis provided with heads, as 11 and 12, ducts 2O 21 lead from the exhaust-port to the opposite ends of the casing, so as to provide a perfect endwise balance of the valve and for the drainage of any Water ofcondensation which may accumulate within the casing.

In the structure described the cylinder-port 15 being constantly in register with the cavity 17 of the valve 16 there is at all times the same pressure within the valve:l cavity as within the cylinder. As the valve is moved to open the induction-port the steam `enters the valve-cavity through a narrow slit, and it is supposed by some that the kick` is due to what might be called a wedge action of the steam tending to widen this slit.

The valve hereindescribed is so constructed that as the induction-port begins to open and the thin sheet of steam rushes into the valve- IOO cavity it impinges against the end wall of this cavity, so that its impact osets the socalled Wedge action just referred to.

I do not undertake to advance a definite theory as to the action by which the valve herein described eliminates the objectionable kick, but believe it to be due either to the continuous communication of the valve-cavity with the cylinder-port or to the described arrangement of the induction-ports of casing and valve or to both combined.

The valve is shown in Figs. 2 and 3 as in its central position-that is to say, with the motor stopped-and preferably, as is shown, the exhaust-port is slightly open, so as to relieve the pressure upon the piston due to the expansihility of the steam and also provide for the drainage of the cylinder when it becomes cool.

' It will be understood that the valves lO and 23 are alike, except in that the one is the reverse of the other. c

I claim as my inventionl. Inan engine-valve, a casing having an induction-port, a cylinder-port, and an exhaust-port between the other two ports, a reciprocating valve having a cavity overlapping the several ports, and a face-section crossing the cavity but spaced'apart from its ends and of sufficient width to simultaneously cover the induction and exhaust ports.

2. In an engine-valve, a cylindrical casing having a cavity overlapping the several ports and prolonged so that it is at all times in register with the cylinder-port, anda face-section crossing the cavity intermediate of its ends and of'suflcient Width to simultaneously cover the induction and exhaust ports.

4. In an engine-valve, a cylindrical casing having induction, exhaust and cylinder ports arranged in the order stated and opening annularly to the chamber of -the casing, and a piston-valve having an annular cavity overlapping the several ports, and a face-ring crossing the cavity intermediate of its ends and of sufficient width to simultaneously cover the induction and exhaust ports.

DE WITT C. PRESCOTT.

Witnesses: c

ARTHUR B. SEIBOLD, E. M. KLATCHER. 

